Picture-drawing data of the printer serving as an output apparatus is stored in a page image memory. A process of writing into the page image memory is conducted as follows. An OR operation or an AND operation is conducted between a bit map data drawn up in accordance with the picture-drawing data supplied from a system such as a personal computer etc. and the data is stored in a write memory, and the data is written into a memory cell depending on a result of the aforementioned operation. When the picture-drawing data is completed and outputted to a printing engine, the aforementioned data is cleared to "0" or "1", which is called clear after read.
In case that a DRAM (Dynamic Random Access Memory) is used as the page image memory, writing into the page image memory (the write memory) is conducted in such a way that the data stored in the write memory is once read, an OR operation or an AND operation is conducted between the write data and the aforementioned read-data in an external operational circuit, and the result of the operation is written back to the write memory.
In general, a printing speed of the printer is greatly dependent on the speed of drawing up the picture-drawing data and storing the same in the page image memory. In terminals of a computer system, the speed of printing of the printer is used to characterize the printer class, and improvement of printing speed is greatly demanded. As a method for elevating the printing speed, improvement of the process of drawing up the picture-drawing data can be thought out. From this point of view, it is expected that improvement of process of storing the picture-drawing data (write into the memory) contributes to elevation of the printing speed.
However, in the conventional semiconductor memory, a remedy for storing the picture-drawing data contributing to improvement of the printing speed is not yet investigated, and the speed of writing into the memory still remains slow.